DYNAMOMETRIC MEASURING PROCEDURES FOR HORIZONTAL BAR AND UNEVEN BARS

  • K. Knoll
  • V. Drenk
  • J. Krug

Abstract

INTRODUCTION -Dynamometric measuring procedures for gymnastics apparatuses are applied to analyse sports technique, to determine load effects on female and male gymnasts and to optimise gymnastics apparatuses. In studies on sports technique dynamometric procedures are mostly applied in combination with kinemetric procedures, especially with photogrammetric procedures. For technique training including feedback information we consider gymnastics apparatus' dynamometers in connection with synchronised video recordings, if possible with frame-grabbing based on external dynamometric signals For the feedback training on horizontal bar and uneven bars adequate dynamometers have been constructed with different modifications to cover several accuracy requests and applications. RESULTS -According to the principle of electric strain measurement reaction forces on horizontal bar and uneven bars are determined in vertical as weil as in horizontal direction. To validate mathematical-physical models of movement simulation additionally the torsion momentum caused by hand friction was monitored using the same measuring principles These measurements do not depend on the working point of force, i.e. of the gripping point of female or male gymnast. In this measuring procedure the measurement strain is influenced by guy strain strength. Therefore strain strength must be known with its initial value. It is monitored by a tractive force transducer which is part of the guy wire. To calculate vertical and horizontal forces for the uneven bars the inclined position of the stake has to be taken into account. The calculated calibration curves (force as a function of measuring strain) are non-linear in the upper loading range In cases in which it is impossible to apply astrain gauge as part of the horizontal bar or the uneven bars kinemetric procedures have been developed to measure forces. These procedures are based on the proportionality between bending and spring force. In a preliminary version a video-camera records with a small frame sector the movement of the bar By digitalizing certain picture points bending of the bar is calculated. Then reaction forces can be determined. In a second version apointer is attached to the bar head. The movement of the pointer top provides the vector dynamograph of reaction force Its magnitude depends on the pointer length. Analysis of pointer movement is done by automatic picture point tracking. CONCLUSION Based on the principle of electric strain measurement and introducing an optimal number of strain gauges accurate dynamometers for the horizontal bar and the uneven bars have been developed. Different strain forces and non-linear calibration graphs have been taken into account. The dynamometers based on kinemetric procedures represent approximations which can be applied to i3 limited extend. Both procedures cannot be applied for immediate evaluation in the sense of feedback
Section
Equipment / Instrumentation